Method for lubricating at least two units of a vehicle equipped with an internal combustion engine

ABSTRACT

The present invention relates to a method for lubricating at least two units of a vehicle having an internal combustion engine, each unit comprising one or more assemblies, and to a corresponding vehicle. In order to be able to dispense with an oil change of the individual units, and at the same time ensure the necessary quality and quantity of lubricant, it is proposed according to the invention to conduct the lubricant in series through the at least two units in that fresh lubricant is fed to the first unit from a container, at least some of the used lubricant is removed from the oil trough of the individual units and is fed to the unit which is respectively arranged afterwards in the series, and the lubricant which is removed from the oil trough of the last unit is fed to the internal combustion engine for combustion.

[0001] The present invention relates to a method for lubricating atleast two units of a vehicle having an internal combustion engine, eachunit comprising one or more assemblies, and to a corresponding vehicle.

[0002] In conventional vehicles with an internal combustion engine, theindividual assemblies such as the transmission, engine, hydraulics, wetbrakes, retarders and the like are lubricated in closed lubricantcircuits which are separated from one another. In order to ensureoptimum lubrication of the lubrication points of the individualassemblies, different lubricants based on mineral oils or partially orcompletely synthetic fluids, which are adapted to the respectivetechnical lubrication requirements of the individual assemblies byadding special additives, are generally used for the various lubricationcircuits.

[0003] In order to reduce the number of different lubricants which arenecessary as a result of this, recently universal lubricants which aremainly suitable for agricultural and forestry vehicles, for example UTTO(Universal Tractor Transmission Oil) and STOU (Super Tractor OilUniversal), which can be used for lubricating a plurality of assemblies,have been developed. Whereas UTTO products can be used for lubricatinghydraulics, transmission and wet brakes, STOU oils are also suitable forlubricating engines. By using such universal lubricants it is possibleto supply a plurality of assemblies, such as hydraulics, transmissionand wet brakes, with a lubricant from a common lubricant circuit, whichlubricant is however structurally separated from the lubricant circuitof the internal combustion engine owing to the different requirementsmade in terms of the purity of the lubricant. Accordingly, such vehicleshave two separate units which are supplied by one isolated lubricantcircuit in each case, specifically on the one hand a unit which iscomposed of the assemblies comprising the hydraulics, transmission andwet brakes, and on the other hand the internal combustion engine.

[0004] All these systems have in common the fact that an oil change hasto be carried out at the individual lubricant circuits at chronologicalintervals because, during the consumption, active ingredients are used,and the lubricant ages and is contaminated with extraneous substances.However, during an oil change, dangerous quantities of waste oil areproduced which have to be disposed of at some cost in accordance withtheir waste rating. In addition, each oil change inevitably requires thevehicle to be stationary for a time and incurs maintenance costs. Inaddition, in vehicles with a plurality of lubricant circuits, differentoil change intervals are often necessary and it is necessary to fill thecircuits with different lubricants, making the logistics of an oilchange more difficult.

[0005] In order to be able to dispense with at least one oil change ofthe engine lubricant circuit, it has recently been proposed to burn usedlubricant continuously or at intervals together with the fuel in theengine. With this type of waste lubrication, use is made of the factthat up to several percentages of oil can be added to the fuel of theinternal combustion engine without adversely affecting the performanceof the engine, said oil then being burnt along with the combustion offuel.

[0006] DE 31 38 144 A 1 discloses a lubricant and fuel circuit, inparticular for the diesel engines of heavy goods vehicles, in which agiven quantity of lubrication oil is periodically extracted from the oiltrough of the engine and fed to the fuel tank in order to burn theextracted quantity together with the customary diesel fuel in theengine. Furthermore, an automatically operating arrangement formonitoring the lubricant level is provided in order to keep it at a setpoint level in the oil trough so that freshly lubricant oil iscontinuously fed into the lubricant circuit and at the same time thewaste oil is periodically cleaned. Only one engine oil change whichgenerally takes place at intervals is therefore avoided by virtue of thefact that a specific quantity of used engine oil is continuouslyreplaced by a corresponding quantity of fresh engine oil, and the usedengine oil is burnt with the fuel.

[0007] DE 30 19 877 A1 discloses a device for changing oil in aninternal combustion engine with a lubrication system and an oil troughand a fuel system with a fuel tank in which, in order to change the oilautomatically and conduct away used lubricant, oil feeding means fortransferring some of the used engine oil from the lubrication system tothe fuel system are provided in order to mix the used proportion of oilwith fuel. Furthermore, the device has an oil tank for storing fresh oilas well as an oil supply means for supplying fresh oil from the oil tankto the lubrication system.

[0008] DE 30 06 903 A1 discloses a method for replacing the lubricationoil collected in the oil sump of an internal combustion engine, using anoil discharge pump which has to be controlled separately, in whichmethod the oil discharge pump adds metered quantities of oil from theoil sump of the internal combustion engine to the fuel of the internalcombustion engine and at least the quantity of fresh oil whichcorresponds to the discharged quantity of oil is fed to the internalcombustion engine. Here, the quantities of oil are dimensioned in such away that the prescribed oil filling quantity is discharged independentlyof the oil consumption of the internal combustion engine within an oilchange interval. The control device is configured in such a way that theoil discharge pump begins to operate only during a fuel filling processduring which the filling level measuring display moves upward within ashort time.

[0009] Finally, WO 99/23365 discloses a method for lubricating andsimultaneously supplying fuel to the internal combustion engine in whicha plant oil which has been treated with additives is continuously fed aslubricant to the internal combustion engine during operation, and theused plant oil lubricant is metered, together with a mixture of freshplant oil and diesel oil or rape seed oil methyl ester in the engine,and burnt as engine fuel.

[0010] Although these methods make it possible to dispense with an oilchange of the engine lubrication circuit, the lubricants for the otherassemblies such as the transmission, hydraulics and the like have to bereplaced at regular intervals with the associated disadvantages. Afurther disadvantage of these methods is the logistical expenditure onsupplying fresh lubricant to the individual lubrication circuits whichare separated from one another.

[0011] The object of the present invention is therefore to makeavailable a method for lubricating all the fluid-lubricated units,however at least two units of a vehicle having an internal combustionengine, in which an oil change is not necessary for the respectiveunits, and nevertheless the necessary quality and quantity of lubricantis ensured.

[0012] This object is essentially achieved with a method of the typementioned at the beginning in that the lubricant is successivelyconveyed through at least two units, in that fresh lubricant is fed tothe first unit from a container, at least some of the used lubricant isremoved from the oil trough of the individual units and fed to the unitwhich is respectively arranged afterwards in the series, and thelubricant which is removed from the oil trough of the last unit is fedto the internal combustion engine for combustion.

[0013] Owing to the common lubrication of all the units with a lubricantand subsequent thermal recycling of the waste oil in the engine, withthe method according to the invention an oil change is no longernecessary in the respective units so that costly disposal of waste oilis dispensed with, and the stationary times of the vehicle which resultfrom this are avoided. In addition, all that is now necessary is to feedfresh oil to the first unit in the series so that the logisticalexpenditure is considerably reduced. Apart from the maintenanceadvantages and the simplified logistics for the operator, this methodensures that, on the one hand, during operation, fresh, or at mostlightly aged lubricant which is still suitable for lubrication, is fedcontinuously to all the units, and, on the other hand, aged lubricant iscontinuously removed from these lubrication circuits so that a lubricantwhich is sufficiently fresh is always available in all the lubricationcircuits for optimum lubrication of the lubrication points. Here, therefreshing rate, that is to say the proportion of the fresh lubricantwhich is fed to the units and of the used lubricant which is removedfrom the lubrication circuits, with respect to the fuel consumption, canbe adapted to the quality of the used lubricant and to the loading towhich the lubricant is subjected overall in all the units.

[0014] The refreshing rate is preferably between 0.1% and 2.5%.

[0015] Furthermore, the units are preferably arranged in accordance withthe degree of their requirement for purity of the lubricant. Thisensures that the unit with the highest requirement of purity is fed withfresh lubricant while the lubricant supply of the units with lowerrequirements is refreshed with partially aged lubricant from the unitwhich was respectively arranged in the preceding position in the seriesbefore the used lubricant is then burnt in the internal combustionengine at the end of the use chain.

[0016] In a tractor with two separate lubrication circuits, specificallyone for hydraulics, transmission and wet brakes and one for the engine,for example fresh lubricant is preferably firstly fed to the unitcomposed of hydraulics, transmission and wet brakes, since in said unitthe purity of the lubricant, a constant coefficient of friction of thewet brake and good wear protection properties are decisive for optimumlubrication. On the other hand, the thermal loading of the lubricant incomparison to the engine is not very high so that no appreciable agingof the lubricant occurs before the oil is removed from this lubricationcircuit and used for lubricating the engine. In the engine, thelubricant is then very heavily loaded in terms of thermal oxidation, anda high degree of charging with pollutants, in particular soot, occurs.

[0017] According to one preferred embodiment of the present inventionthere is provision that additives are added to the lubricant removedfrom a unit before said lubricant is supplied to the unit which followsin series. Such adding of additives is expedient especially after thelubricant has passed through the unit which is critical in terms of thecoefficient of friction and in which the lubricant is particularlystressed, for example in order to supplement additives such asantioxidants, wear protection additives or the like, which have alreadybeen decomposed. Although all the units of a vehicle can basically belubricated with one lubricant, the technical requirements made of theseuniversal oils are very high since the individual units make differentrequirements of the lubricant. On the one hand, for example theperformance level of an HLP hydraulic oil is required for a hydraulicoil, and on the other hand, the vehicle transmission is to be suppliedwith a lubricant according to GL-4 or the like. In addition to theserequirements for aging stability, wear protection, viscosity temperaturebehavior, air release capability and corrosion protection, wet brakingand synchronizations as well as automatic transmissions additionallyproduce very specific requirements in terms of the coefficients offriction. As a result of the inventive addition of additives, thelubricant which is conveyed through all the units can be optimized tothe requirements of the next unit. For example, dispersants anddetergents are essential to keep the internal combustion engine clean,but on the other hand are not necessary in the transmission circuit andhydraulic circuit. For example, it is conceivable to optimize an UTTOoil after use in the engine lubrication circuit after use in the commontransmission and hydraulic sump of a tractor by adding dispersants,detergents and further additives, in particular additives for protectingthe engine against charging with acid combustion gases, and forprotecting against the formation of surface coatings, mud and deposits.

[0018] The additives are preferably added directly into the oil troughof the unit or into the oil line leading to the unit, by means of anautomatic device, metering pump or the like.

[0019] In order to avoid increased emissions after the lubricant hasbeen burnt in the engine, lubricants which are suitable for also beingburnt in the engine and which are, if appropriate, treated withadditives, in particular ash--free and heavy-metal-free, low-sulfur andlow-phosphorus formulations are used for lubricating the assemblies. Forthis purpose, in particular lubricants based on plant oils have provensuitable, it being possible to compensate for the aging stability ofthese plant lubricants, which is lower in comparison with mineral oils,by increasing the refreshing rate.

[0020] In order to remove the used lubricant from the last unit in theseries, it is possible to burn it in the engine together with the fuel.This has the advantage that the lubricant is also used as a fuel. Inorder to mix the burnt lubricant with the fuel, the lubricant can befed, for example, to the fuel line, specifically preferably before thefuel filter, in order to retain any pollutant in the used lubricant.

[0021] Alternatively to this, small quantities of waste oil can also bedisposed of by means of direct injection into the hot exhaust section ofthe internal combustion engine. Here, at temperatures of more than 500°C., auto-ignition occurs so that the waste oil burns with the impuritiescontained in it without possibly disruptive additives, particles or thelike being able to cause problems in the engine.

[0022] The burning of waste oil preferably takes place in proportion tothe fuel consumption in order to keep the vehicle emissions at aconstant rate. Alternatively, it is possible to provide for the wasteoil also to be burnt only in specific engine states, for example onlywhen there is a full load or partial load of more than 70%, or toregulate the refreshing rate of the lubricant in all the units as afunction of the signal of an oil state sensor. For example, theviscosity can serve as a criterion for the oil state for a vehicle whichis lubricated with a lubricant which is based on rape seed oil. In thisvariant, the refreshing method is then activated when a specificlimiting value of the viscosity is exceeded, by removing some of theused oil from the respective unit and replacing it with fresher oil. Forother lubricants it is also possible to use one or more other lubricantparameters to regulate the refreshing rate.

[0023] In a development of the inventive idea it is proposed-always tomaintain an essentially constant quantity of lubricant in all the unitsinvolved, for example by monitoring the supply of fresh oil anddischarge of waste oil, in order to ensure that there is uniform andreliable lubrication.

[0024] The lubricant is preferably fed through the series composed of areservoir container for fresh lubricant, first to last unit to belubricated and a fuel line or exhaust section of the engine, by means ofelectric, mechanical or hydraulic metering pumps, self-venting pumpsbeing particularly preferably used. According to the invention, thepumps can both be activated and regulated individually and operated in amechanically or electronically coupled fashion. It is also possible touse electric or mechanically or hydraulically activated valves tocontrol the flow of oil for the refreshing process.

[0025] According to a further embodiment of the present invention, afilling level measuring device is assigned to all the units, or to aselection of units, which filling level measuring device can be used tocontrol the corresponding metering pumps and/or valves in such a waythat the volume of oil or the oil level in the units is prevented fromdropping or being exceeded. A central control device preferablyregulates all the pumps, valves etc. and for this purpose evaluates allthe signals of the filling level measuring device and, if appropriate,further sensors. According to the invention, it is also possible tointegrate all the metering pumps, valves and the regulating electronicswhich are necessary for the described method into the on-boardelectronics of the vehicle, said integration permitting, for examplewhen vehicles are first equipped, an integrated design of thelubrication system. Lubricant, i.e. the mixture of fresh oil and wasteoil which occurs in the units, can be continuously discharged from allthe units, this mixture preferably being discharged at the point wherethe contamination of the oil is highest. In this way, the highestpossible degree of purity of the oil is always achieved in therespective unit.

[0026] The method according to the invention is suitable in principlefor all types of vehicles, in particular for land vehicles andwatercraft. Tractors, which have, as units to be lubricated, on the onehand an engine and, on the other hand, a unit composed of the assembliescomprising the hydraulics, transmission and wet brakes, constructionmachinery having the units comprising an engine, transmission andhydraulics, buses and trucks having the units comprising an engine,transmission and retarder, passenger cars, ships and boats having aseparate transmission circuit and engine oil circuit as well as fixedengines with a common coolant circuit and engine oil circuit are citedby way of example as application examples, in a non-restrictive fashion.

[0027] One particular advantage of the method according to the inventionis that the structural measures which are necessary for it can be takeninto account not only when new vehicles are manufactured but can also becorrespondingly retrofitted in used vehicles.

[0028] A further object of the present invention is a vehicle which issuitable in particular for carrying out the method described above andwhich has an internal combustion engine.

[0029] According to the invention, the vehicle with internal combustionengine has a reservoir container for fresh lubricant, at least two unitsto be lubricated, each unit comprising one or more assemblies and havingan oil trough, a fuel tank and a fuel line for feeding fuel into theinternal combustion engine, at least two of the units being arranged ina series in such a way that a feed line for fresh lubricant leads fromthe reservoir container to the first assembly in the series, a lubricantline leads in each case from the unit arranged in the preceding positionin the series to the unit arranged afterwards in the series, and adischarge line for used lubricant leads into the fuel line or theexhaust section of the internal combustion engine from the last unit inthe series.

[0030] According to one particular embodiment of the present invention,the vehicle additionally has at least one additive tank from which anadditive line leads into a lubricant line which leads to at least oneunit, or alternatively leads directly into the oil trough of a unit. Bymeans of the metered addition of additives, the lubricant which isconveyed through all the units can be optimized to the requirements ofthe corresponding units.

[0031] In one development of the inventive idea, it is also proposed toequip at least one of the lubricant lines with a metering pump via whichthe lubricant is fed through the corresponding lubricant line.

[0032] In addition, at least one of the units can have an automaticfilling level measuring device which, if appropriate via a controldevice, to the metering pump or pumps, and thus permits the refreshingrate to be controlled and the lubricant filling level in the individualunits to be controlled.

[0033] In addition or alternatively to the at least one automaticfilling level measurement device it is possible to provide, also forcontrolling the refreshing rate, an oil state sensor which is connected,if appropriate via a control device, to the metering pump or pumps andthus permits the refreshing rate to be controlled as a function of thelubricant quality.

[0034] According to one particular embodiment of the present invention,the vehicle has a central control device which evaluates the measuredvalues of the or of the filling level measuring device and/or oil statesensors and converts them into a control signal by means of which themetering pump or metering pumps are controlled. Moreover, the controldevice can be connected to the on-board electronics or other vehiclecomponents in such a way in order to call additional information there,for example load, engine speed, oil temperatures, current fuelconsumption, and to use this information to control the metering pump ormetering pumps.

[0035] Further objectives, features, advantages and applicationpossibilities of the invention emerge from the following description ofexemplary embodiments with reference to the drawing. Here, all thefeatures described and/or illustrated graphically form, in themselves orin any desired combination, the subject-matter of the invention, evenindependently of their combination in individual claims or their backreference.

[0036] The single figure is an exemplary schematic view of a vehicle forcarrying out the method.

[0037] The vehicle has a reservoir container 1 for fresh lubricant, anadditive tank 2 and three units 3 a, 3 b and 3 c to be lubricated, theunit 3 a which is arranged first in the series being, for example, thehydraulics, the second unit 3 b being the transmission and the thirdunit being the engine 3 c. All three units 3 a, 3 b and 3 c arelubricated by circulation lubrication, the lubricant collecting in therespective oil troughs 4 a, 4 b, 4 c after it passes through thelubrication points.

[0038] A lubrication line 5 a which is equipped with a metering pump 6 aleads from the reservoir container 1 to the first unit 3 a in theseries, through which line fresh lubricant can be continuously ordiscontinuously fed to said first unit 3 a. In addition, the first unit4 a is connected to the second unit 4 b, and the second unit 4 b isconnected to the third unit 4 c, in each case via a lubricant line 5 b,5 c which is equipped with a metering pump 6 b, 6 c and through whichlubricant can be fed from the respectively preceding unit 4 a, 4 b tothe respectively following unit 4 b, 4 c. Finally, the lubricantdischarge line 5 d which is equipped with a metering pump 6 d leads fromthe third unit 4 c either into the exhaust section of the engine 7 orinto the fuel line (not illustrated in the drawing) in order to burn theextracted, used lubricant in the engine. While the lubricant lines 5 b,5 c and 5 d open, with their removal side, into the bottom of therespective oil troughs 4 a, 4 b and 4 c so that as far as possibleselectively used lubricant is extracted from the units 3 a, 3 b and 3 c,the supply sides of the lubricant lines 5 a, 5 b and 5 c each open intoa region which is spatially separate there from, for example at a pointwhich is arranged above the lubrication points, in order to prevent asfar as possible fresh lubricant, or lubricant which has been subjectedto little aging, being removed from the units 3 a, 3 b and 3 c throughthe lubricant lines 5 b, 5 c and 5 d. Furthermore, an additive line 8which leads from the additive tank 2 to the lubricant line 5 c whichconnects the second and third units 4 b, 4 c is provided and it can beused by the metering pump 9 to pump additives into the third unit 3 cvia the line 5 c. In the oil trough or the oil sump (4 a, 4 b and 4 c)of the units 3 a, 3 b and 3 c, in each case a filling level measuringdevice 10 a, 10 b and 10 c is provided, which devices are connected viacontrol lines 11 to a central control device 12. The control device 12receives the filling level signals of all the units via the controllines 11 and can also control the metering pumps 6 a, 6 b, 6 c and theadditive pumps 9 via control lines 11 in such a way that the oil leveland the additive content in the units always correspond to the necessarylevel. If, for example, the oil level in unit 3 b drops below thedefined minimum value, the metering pumps 6 a and 6 b receive acorresponding control signal for the continued supply of lubricant untilthe oil level in the unit 4 b corresponds to the set point level again.As a result, manual monitoring of the oil level in the individual unitsbecomes superfluous. The oil change of all the individual units whichhas to be carried out at periodic intervals and which is necessary withconventional lubrication is also eliminated so that only the content ofthe fresh oil supply container 1 and, if appropriate, of the additivetank 2 has to be regularly replaced. For this purpose, a levelmonitoring system (not illustrated) can be provided in the two reservoircontainers 1 and 2. In addition to the filling level, the refreshing ofthe oil in the individual units 3 a, 3 b and 3 c is also regulated bymeans of the control device 12 in that a quantity of oil whichcorresponds to the refreshing rate is removed from the unit 3 c by meansof the metering pump 6 d, and the oil level in all the units is adjustedwith the metering pumps 6 a, 6 b and 6 c, and the corresponding quantityof additive is fed to the unit 3 c via the metering pump 9. In general,small quantities of oil are removed continuously or quasi-continuouslyfrom the units 3 a, 3 b and 3 c for refreshing in order to keep thefluctuations in the filling level as small as possible. The refreshingrate can be constant over time here or be regulated as a function ofvarious influencing variables. For example, the quantity of waste oilwhich is burnt with the fuel can be set in proportion to the fuelconsumption in that the current fuel consumption is signaled to thecontrol device 12 by the injection pump or the motor vehicle on-boardelectronics via a control line (not illustrated). It is also possible tocarry out adaptation to the load state of the units in this way.Alternatively or in addition to this, oil state sensors 13 a, 13 b and13 c may be provided in order to monitor the lubricant state in theunits 3 a, 3 b and 3 c. In this way it is possible, when a specificlimiting value for the oil state is exceeded, determined for example bymeans of a parameter such as viscosity, dielectric constant or the like,to selectively replace some of the used oil in all the units 3 a, 3 b, 3c by means of the metering pumps 6 a, 6 b, 6 c, 6 d and 8. Basically,the waste oil which is intended to burn with the fuel should be meteredinto the fuel by the control device in such a way that the stressing ofthe environment is minimized. This is preferably carried out in such away that the used lubricant is continuously metered into the fuel up toa maximum proportion at which permissible emission values are not yetexceeded. A buffer tank may be provided for buffering an excess of usedlubricant which occurs under certain circumstances for a brief time.

List of Reference Symbols

[0039]1 Reservoir container for fresh lubricant

[0040]2 Additive tank

[0041]3 a-c Unit

[0042]4 a-c Oil trough

[0043]5 a-d Lubricant line

[0044]6 a-d Metering pump of the lubricant line

[0045]7 Exhaust section of the engine

[0046]8 Additive line

[0047]9 Metering pump for adding additives

[0048]10 a-c Filling level measuring device

[0049]11 Control line

[0050]12 Control device

[0051]13 a-c Oil state sensor

1. A method for lubricating at least two units of a vehicle having aninternal combustion engine, each unit (3 a, 3 b, 3 c) comprising one ormore assemblies, characterized in that lubricant is successivelyconveyed through the at least two units (3 a, 3 b, 3 c) in that freshlubricant is fed to the first unit (3 a) from a container (1), at leastsome of the used lubricant is removed from the oil trough (4 a, 4 b, 4c) of the individual units and is fed to the unit (3 b, 3 c) which isrespectively arranged afterwards in the series, and the lubricant whichis removed from the oil trough (4 c) of the last unit (3 c) is fed tothe internal combustion engine for combustion.
 2. The method as claimedin claim 1, characterized in that the refreshing rate of lubricant is0.1% to 2.5% with respect to the fuel consumption.
 3. The method asclaimed in claim 1, characterized in that the units (3 a, 3 b, 3 c) arearranged in accordance with the degree of their requirement for purityof the lubricant.
 4. The method as claimed in claim 1, characterized inthat additives are added to the lubricant removed from the unit (3 a, 3b), before it is fed to the unit (3 b, 3 c) which follows in the series.5. The method as claimed in claim 4, characterized in that the additivesare input directly into the oil trough(, 4 b, 4 c) of the unit or intothe lubricant line (5 b, 5 c) which leads to the unit (3 b, 3 c).
 6. Themethod as claimed in claim 1, characterized in that ash-free andheavy-metal-free, sulfur-free and low-phosphorus formulations on thebasis of plant oils are used as lubricants.
 7. The method as claimed inclaim 1, characterized in that the lubricant which is removed from theoil trough (4 a, 4 b, 4 c) of the last unit (3 c) is burnt in theengine, together with fuel supplied from a fuel tank.
 8. The method asclaimed in claim 1, characterized in that the lubricant which is removedfrom the oil trough (4 a, 4 b, 4 c) of the last unit (3 c) is fed, orsprayed, for the purposes of combustion, into the exhaust section of theengine (7).
 9. The method as claimed in claim 1, characterized in thatthe lubricant which is removed from the last unit (3 c) is burnt in theengine, at least essentially in proportion to the fuel consumption. 10.The method as claimed in claim 1, characterized in that the lubricantwhich is removed from the last unit (3 c) is burnt in the engine onlywhen there is a full load or partial load of more than 70% of theengine.
 11. The method as claimed in claim 1, characterized in that anessentially constant quantity of lubricant is continuously maintained inthe units affected.
 12. The method as claimed in claim 1, characterizedin that the lubricant is fed through the series composed of thereservoir container for fresh lubricant (1), first to last unit (3 a, 3b, 3 c) to be lubricated, and the fuel line or the exhaust section ofthe engine (7), by means of electric, mechanical or hydraulic meteringpumps (6 a, 6 b, 6 c, 6 d).
 13. The method as claimed in claim 1,characterized in that the corresponding metering pumps (6 a, 6 b, 6 c, 6d) are controlled by a control device (12) which receives and evaluatessignals of filling level measuring devices (10 a, 10 b, 10 c), in such away that the lubricant level in the units is prevented from dropping orbeing exceeded.
 14. A vehicle having an internal combustion engine, inparticular for carrying out the method as claimed in claim 1, having areservoir container (1) for fresh lubricant, at least two units (3 a, 3b, 3 c) to be lubricated, each unit (3 a, 3 b, 3 c) comprising one ormore assemblies and having an oil trough (4 a, 4 b, 4 c), a fuel tankand having a fuel line for feeding fuel into the internal combustionengine, characterized in that at least two of the units (3 a, 3 b, 3 c)are arranged in series in such a way that a feed line for freshlubricant (5 a) leads from the reservoir container (1) to the first unit(3 a) in the series, in each case a lubricant line (5 b, 5 c) leads fromthe unit (3 a, 3 b) which is arranged in the preceding position in theseries, to the unit (3 b, 3 c) which is arranged afterwards in theseries, and a discharge line for used lubricant (6 d) leads into thefuel line or the exhaust section (7) of the internal combustion enginefrom the unit (3 c) which is last in the series.
 15. The vehicle asclaimed in claim 14, characterized in that at least an additive tank (2)is provided, from which an additive line (8) leads into a lubricant line(5 a, 5 b, 5 c) which leads to at least one unit (3 a, 3 b, 3 c), orinto the oil trough (4 a, 4 b, 4 c) of a unit (3 a, 3 b, 3 c).
 16. Thevehicle as claimed in claim 14, characterized in that at least one ofthe lubricant lines (5 a, 5 b, 5 c, 5 d) is equipped with a meteringpump (6 a, 6 b, 6 c, 6 d).
 17. The vehicle as claimed in claim 16,characterized in that at least one of the units (3 a, 3 b, 3 c) has anautomatic fuel level measuring device (10 a, 10 b, 10 c) which isconnected, if appropriate via a control device (12), to the meteringpump or pumps (6 a, 6 b, 6 c, 6 d, 8).
 18. The vehicle as claimed inclaim 16, characterized in that at least one of the units (3 a, 3 b, 3c) has an oil level sensor (13 a, 13 b, 13 c) which is connected, ifappropriate via a control device (12), to the metering pump or pumps (6a, 6 b, 6 c, 6 d, 8).
 19. The vehicle as claimed in at least to claim16, characterized in that a central control device (12) is providedwhich evaluates the measured values of the filling level measuringdevice or devices (10 a, 10 b, 10 c) and/or of the oil state sensors (13a, 13 b, 13 c), and converts them into a control signal by means ofwhich the metering pump or metering pumps (6 a, 6 b, 6 c, 6 d, 8) arecontrolled.
 20. The vehicle as claimed in claim 19, characterized inthat the control device (12) is configured in such a way that additionalinformation such as load, engine speed, oil temperatures, current fuelconsumption, can call from the on-board electronics or other vehiclecomponents and can use to control the metering pump or metering pumps.